Problem: If $a + b + c = 10$ and $x + y = -8$, what is $-10a - 10b - 10c - 5y - 5x$ ?
Answer: $= -10a - 10b - 10c - 5x - 5y$ $= (-10) \cdot (a + b + c) + (-5) \cdot (x + y)$ $= (-10) \cdot (10) + (-5) \cdot (-8)$ $= -100 + 40$ $= -60$